Detection of Ultraviolet Emission Lines in SN1006 with the Hopkins Ultraviolet Telescope

John C. Raymond

Harvard-Smithsonian Center for Astrophysics, 60 Garden St.,
Cambridge, MA 02138
raymond@cfa.harvard.edu

William P. Blair

Department of Physics and Astronomy, Johns Hopkins University
Charles and 34th Streets, Baltimore, MD 21218
wpb@pha.jhu.edu

and

Knox S. Long
Space Telescope Science Institute, Baltimore, MD 21218
long@stsci.edu

Abstract:

The Hopkins Ultraviolet Telescope was used during the Astro-2 space shuttle mission in 1995 March to observe emission lines of H I, HeII , CIV , NV , and OVI from the faint optical Balmer line filament at the northwest edge of the SN1006 supernova remnant. This is the first successful far ultraviolet observation of a nonradiative shock wave with velocity in excess of 300 , and the first detection of ultraviolet emission lines from SN1006. The observed line widths are consistent with the 2300 width reported for H , implying that the velocities of different ions are independently randomized in the shock and that ion-ion temperature equilibration is ineffective. A faint continuum in the spectrum is consistent with relatively strong dust-scattered starlight along this line of sight, visible because of the large HUT spectrograph aperture used for this observation. The relative line intensities are in reasonable agreement with existing model predictions for a 2300 shock. However, proton excitation rates may compete with electron excitation in producing the emission lines and needs to be included in the model calculations before a comprehensive analysis can be attempted.

Subject headings: ISM: Individual (SN1006) -- ISM: Supernova Remnants -- Shock Waves -- Ultraviolet: ISM



raymond@cfa.harvard.edu